A boost converter, also known as a step-up converter, is a power converter with an output DC voltage greater than its input DC voltage. It is a class of switching-mode power supply containing at least a first electronically controlled switch (e.g., a transistor), at least a first energy storage element (e.g., an inductor), and an additional element such as a diode or a second electronically controlled switch. Typically, the electronically controlled switches and diode are arranged between the inductor and the output, with current being alternately drawn to charge the inductor responsive to the first electronically controlled switch being closed, and passed to a load responsive to the first electronically controlled switch being open. The current goes through the diode or the second electronically controlled switch when it is passed to the load.
A buck converter, also known as a step-down converter, is a power converter with an output DC voltage less than its input DC voltage. It is a class of switching-mode power supply containing at least a third electronically controlled switch (e.g., a transistor), at least a second energy storage element (e.g., an inductor), and an additional element such as a diode or a fourth electronically controlled switch. Typically, the electronically controlled switches and diode are arranged between the input DC power source and the inductor, with current being alternately drawn to charge the inductor through a load responsive to the third electronically controlled switch being closed, and continued to the load discharging the inductor responsive to the third electronically controlled switch being open. The diode or the fourth electronically controlled switch is in series with the inductor when the inductor is discharging to the load.
A classical or a cascaded buck-boost converter, is a power converter with an output DC voltage which can be greater than or less than the input DC voltage. It is a class of switching-mode power supply containing at least two electronically controlled switches, at least one energy storage element (e.g., an inductor), and additional elements such as diodes and/or additional electronically controlled switches. Typically, each terminal of the inductor is coupled to at least one electronically controlled switch.
Both the boost converter and the cascaded buck-boost converter of the prior art exhibit a right-half plane zero in a control to output transfer function when stepping up voltage in a continuous conduction mode. This means, that when a load increases its current draw, a feedback loop of the converter senses a decrease in an output and attempts to compensate by increasing the output. Unfortunately, in an initial stage, the output current drops. For example, a duty cycle is increased to increase a charge time of an inductor to compensate for the increased load. However, until a full switching cycle has passed, the increase in duty cycle results in a decreased discharge time for the inductor, since a period of the switching cycle does not change. The decreased discharge time results in an initial decrease in the output which reinforces the decrease in the output due to the increased load. In order to ensure stability, it is thus necessary to include a relatively low frequency dominant pole into a control loop. The need for such a low frequency dominant pole places an upper limit on a dynamic performance of the converter.